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auto-negotiation

 

Syntax

Hierarchy Level

Release Information

Statement introduced in Junos OS Release 11.1 for the QFX Series.

Statement introduced in Junos OS Release 14.1X53-D20 for the OCX Series.

Description

Explicitly enable or disable autonegotiation. Autonegotiation is enabled by default, and will autonegotiate the speed with the link partner. We recommend that you keep autonegotiation enabled for interfaces operating at 1G and 10G.

(For QFX5100-48T only) To negotiate any speed on QFX5100-48T switches:

set interfaces xe-0/0/0 ether-options auto-negotiation

set interfaces xe-0/0/0 speed auto

Basically, when you configure a port using speed auto option, the port deletes the last configured speed, comes up again and advertises all the possible speeds:

For a port to start with a specific speed, it is mandatory that both the auto-negotiation must be enabled and interface must be configured with a particular speed. Otherwise, the switch will remain with the last negotiated speed. If you only set the auto-negotiation option (and no speed option), then the switch will start with the last speed it connected at and will only advertise that to the server.

To configure a particular speed on QFX5100-48T switches, mention the speed:

set interfaces xe-0/0/0 ether-options auto-negotiation

set interfaces xe-0/0/0 speed speed

For example to configure 1-Gbps speed in full duplex mode, execute the following command:

set interfaces xe-0/0/0 ether-options auto-negotiation

set interfaces xe-0/0/0 speed 1g

Note that you can not disable auto-negotiation on 1-Gigabit Ethernet ports. It is mandatory to enable autonegotiation when 1-Gbps speed is configured on a particular interface.

If you set the speed option to 1g or 10g, the auto-negotiation option is enabled by default, since you can not turn it off at those speeds and the switch will only advertise that one single speed.

Note

On QFX5100-48T-6Q switches, autonegotiation is not supported for 100-Mbps speed.

  • auto-negotiation—Enable autonegotiation.

  • no-auto-negotiation—Disable autonegotiation. When autonegotiation is disabled, you must explicitly configure link mode and speed options.

Required Privilege Level

interface—To view this statement in the configuration.

interface-control—To add this statement to the configuration.